Here's a breakdown:
* Spanish:
* Las mochilas (feminine plural) - This is the most common usage for "backpacks" in Spanish.
* Portuguese:
* As mochilas (feminine plural) - Similar to Spanish, "mochilas" is feminine in Portuguese.
However, if you're talking about "mochilas" in another language, you'll need to adjust the article accordingly.
For example, in Italian, "mochilas" would become "le mochilas".
Please provide the language you're using, and I can give you the specific definite article.